Various techniques have been suggested for modifying the handle of a toothbrush to facilitate better manipulation of the brush during use. For instance, U.S. Pat. No. 2,179,266 to Lukenbill describes a grip attachment in the form of a tubular sleeve containing opposed bearing portions for engaging the thumb and index finger of the user's hand. In one embodiment, the attachment is fabricated from a rubber-like material which allows the tubular sleeve to be stretched over the toothbrush handle and frictionally engage the underlying surfaces of the handle. Each of the bearing surfaces on the sleeve have an area which is larger than that of the handle, which makes it easier for the user to grip the toothbrush.
U.S. Pat. No. 4,283,808 to Beebe also describes a detachable gripping device for a toothbrush. The device consists of an elongated plastic foam body having a diameter which can be readily gripped by the user of the toothbrush. The plastic body also includes a centrally disposed longitudinal slot adapted to receive and engage the toothbrush handle.
Gripping devices which are not detachable, but integrally formed in the toothbrush handle, have also been suggested. U.S. Pat. No. 2,094,240 to Herrick, et al., describes a toothbrush handle having a pair of shallow cavities disposed in an opposed configuration to receive the thumb and index finger of the user. The floor of each cavity contains a plurality of grooves, which form a non-slip surface for engagement by the user's finger and thumb.
Other techniques for providing a non-slip surface on a toothbrush include texturing selected portions of the handle. For example, U.S. Pat. No. 4,137,593 to Porper describes a toothbrush handle with a serrated or ribbed surface. The serrated or ribbed surface is formed on the portion of the toothbrush handle that is engaged by the user's thumb. U.S. Pat. No. 4,672,706 to Hill also describes a toothbrush handle which is textured to provide a non-slip gripping surface. The textured portion of the handle has a substantially elliptical cross-section and the texturing extends around the entire periphery of the handle.
Toothbrushes having a handle portion fabricated from two different materials are also known. U.S. Pat. No. 5,054,154 to Schiffer, et al., describes a toothbrush having a handle and a bristled head which are connected by a neck portion. A series of clearances, slots or grooves, filled with an elastic, rubbery material, are formed in the portion of the handle adjacent the neck. The filling of these clearances, slots or grooves with the rubbery material takes place after the toothbrush handle and head have been manufactured. These rubber-filled areas form an elastic, flexible zone in the toothbrush which causes the bristled head to deflect or move out of the way when excessive force is used to brush the teeth. This feature is said to prevent injury to the gums and teeth in the event of excessive brushing pressure.
Toothbrushes having raised rib portions on the handle have also been suggested. U.S. Design Pat. Nos. 318,716 and 324,775 to Kreisher, et al., are examples of such toothbrushes. These ribs are often fabricated from a material which is different from the remainder of the toothbrush. Toothbrushes containing raised rubber ridges or dimples are commercially available.
A fully automated process for forming toothbrush handles from separate or different colored materials is described in an article entitled "Zahoransky's Fully Automatic Two-Color Mold," Brossa press, 1989. This automated process avoids the need to mount or paste the second material, such as rubber, manually onto the toothbrush handle. In the first step of the process, the plastic material which forms the bulk of the toothbrush is vertically injected into the cavity of the mold. The resulting structure is a partially formed toothbrush having a handle with a series of void spaces. The partially formed toothbrush is then automatically moved into a second cavity within the same mold, where a second or different colored material is injected horizontally to complete the toothbrush handle. The second mold cavity is generally contoured so that raised ribs or dimples are formed on the toothbrush handle to provide a non-slip surface. Generally, the first material forming the bulk of the toothbrush is polypropylene while the second material is Santoprene.RTM. rubber. The same material, but colored with two different pigments, may also be used in the process to form a multi-colored toothbrush.
The second material injected into the partially formed toothbrush fuses with the polypropylene or other material forming the bulk of the handle. This second material cannot be torn from the handle, and remains durable for the lifetime of the article.
These automated two-color or two-material molds produce bicomponent toothbrushes of good quality. However, the capital investment for this equipment is significant, so it is generally only used in manufacturing facilities where the level of output justifies the capital cost. In plants where there is insignificant volume to justify this level of capital investment, a need has developed for a bicomponent toothbrush having a non-slip handle which can be manufactured with conventional molding equipment.